Shock-resisting thermallyresponsive device



March 21, 1950 J. TOTH ETAL SHOCK-RESISTING THERMALLY-RESPONSIVE DEVICE Filed July 20, 1946 INVENTORS Gerald JFT'eese and Julius To fh.

ATTORNEY Patented Liar. 21, rest SHOCK-RESISTING TIIEBMALLY- BESPONSIVE DEVICE Julius 'loth and Genlllll'reesalastlcxeesport. Pa... assignors to Westinghouse Electric Corporation, East Pittsburgh, 2a., a corporation tion Pennsylvania Application July 2., 1m, Serial No. 685,.

5 Claims. (Cl. 200-118) This invention relates to circuit breakers, and more particularly to circuit breakers of the type that are controlled by thermally responsive trip elements.

One object of the invention is to provide a circuit breaker with an improved thermally responsive trip device having novel means [or preventing tripping oi the breaker in response to mechanical shocks.

Another object of the invention is to provide a circuit breaker having a thermally responsive trip element with novel means for preventing tripping movement of said thermally responsive element in response to sudden shocks.

Another object of the invention is to provide a circuit breaker with a novel shock-proof thermally-responsive trip device.

Another obiect of the invention is to provide a circuit breaker having a bimetallic trip element with means supporting both sides of said bimetallic element to prevent movement thereof in response to sudden shocks.

Another object or the invention is to provide a circuit breaker having a bimetallic trip element which deflects when heated a predeter mined amount to trip the breaker with means supporting each side of said bimetallic element to prevent tripping movement thereof in response to sudden shocks but which means deflects with said bimetallic element without imposing any additional load thereon.

V The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation. together with additional objects and advantages thereof, will be best understoodfrom the following detailed description of one embodiment thereof when read in conjunction with the accompanying drawing, in which:

Fi ure 1 is a longitudinal sectional view of a circuit breaker embodying the principles oi the invention, one of the supporting plates for the breaker mechanism being removed to more clearly illustrate the mechanism, the breaker mechanism being shown in the closed circuit position, and

Fig. 2 is a sectional view showing a modification of the trip device.

Referring to the drawing, the circuit breaker is illustrated as being mounted in a casing of molded insulating material. The casing comprises'a base portion 2 and a cover portion I secured together by bolts 8 .(only one being 2 shown) through aligned openings Pr vided in each of the casing portions.

The circuit breaker mechanism is supported generally between a pair of spaced support plates Ill within the casing 2-4. The support plates It (only one being shown) are disposed adjacent the side walls of the and each plate is provided with integral extensions II which project through suitable openings in the bottom wall of the base portion 2 of the casing and are riveted over as at I! to secure the support plates in the casing. The support plates it are also secured together by means of spacing studs I! and ii to prevent relative movement of the plates.

A movable contact bar 22 is supported between the plates l0 and is provided with a slot II for cooperating with a pivot pin i6 mounted in the support plates II. A movable contact 24 is mounted on the free end of the contact bar 22 for cooperating with a fixed contact 26 secured by means of a rivet 28 to the bottom wall oi the casing 2. The rivet 28 also serves to secure a terminal conductor 30 to the outside of the casing. The terminal conductor ill is provided 25 with a terminal screw 32 by means of which a circuit conductor may be electrically connected to the breaker. The contact bar 22 is biased by means of a spring 34 in a direction to cause the bottom of the slot 20 to engage the pivot pin II. The spring 34 engages a projection 38 on the contact bar 21 and is compressed between the contact bar and a recess 36 in the bottom wall of the casing.

A releasable member Iii is supported by means of a pivot pin ll extending between and supported by the support plates ll. The releasable member ll is normally restrained in operative position by a latching nose I! vthereon engaging a latch H. The latch H is rigidly secured to a latch member l6 pivotally mounted on a pivot pin 45 supported in the side plates II. The latch member II is biased to latching position by means of a spring 49 coiled about the pivot pin 45. The spring 49 has one end hooked in an opening in the latch member l6 and the other end bearing against the spacing stud IS. The latch member 48 is adapted to be operated to release the member II by a bimetal element It in a manner to be described hereinafter.

The actuating mechanism for the movable contact bar 22 is connected between the releasable member ll and the contact bar. The actuating mechanism comprises a toggle including a toggle link 41 pivotally connected by means of a pivot pin ll to the releasable member I and a toggle 3 link 62 pivotally connected to the movable contact bar 22 by means of a pivot pin 54. The toggle links 41 and 52 are pivotally connected together by means of a knee pivot pin 66.

In order to actuate the toggle 41-52 to effect manual opening and closing of the contacts, there is provided a pair of actuating levers 66 having their inner ends pivotally mounted in the rounded inner ends of V-shaped notches in the supporting plates 16. The actuating levers 56 are rigidly connected together at a point near the outer ends thereof by a connecting rivet 62, and the inner ends" of the levers 66 are retained in their respective notches 66 by means of plates 66 (only one being shown) secured to the support plates Hi. A pair of overcenter springs 64 (only one being shown) is connected between the knee pivot pin 66 of the toggle 41-52 and the connecting rivet 62 of the actuating levers, for the purpose of actuating the toggle and consequently the contact bar 22 with a snap action upon movement of the actuating lever 66.

In the closed position of the circuit breaker, the toggle 4'|62 is overcenter and the overcenter springs 64 hold a spacing washer 5| on the knee pivot pin 60 in engagement with the adjacent edge of an angular portion 65 of the releasable member 46, thus limiting the overcenter position of the toggle. When it is desired to open the breaker contacts, the actuating lever 66 is pivotally moved to the left or in a counterclockwise direction from the position shown to carry the upper ends of the over-center springs past the toggle pivot 46. As soon as this occurs, the springs 64 cause the toggle 41-52 to collapse to the left and moves the contact bar 22 to separate the contact 24 from the fixed contact 26. In the closed circuit position, the toggle 4l52 is effective to stress the spring 34 so that the bot tom of the slot 26 in the contact bar 22 is spaced away from the pivot pin [6. The spring 34 thus biases the contact bar 22 about the pin 54 and applies pressure to the contacts 24 and 26. During an opening operation the spring 34 first moves the adjacent end of the contact bar relative to the pivot pin l6 until the bottom of the slot 26 engages the pin. Thereafter the contact ing. During this movement of the actuating lever 66, the overcenter springs 64 pass the pivot pin 46 and become effective to straighten the toggle 41-52 thus rotating the contact bar 22 clockwise about the pivot pin l6 until the contact 24 engages the fixed contact 26. Thereafter the contact bar 22 rotates slightly counterclockwise about the point oi engagement of the contacts compressing the spring 34.

The bimetal element 66 is formed from a bimetal strip and is constructed in a well-known manner of a pair of laminations having, respectively, high and low thermal coefllcients of expansion, with the strip arranged so that the lamination having the higher coefllcient of expansion is on the inside or right-hand side as viewed in the drawing. The lower end of the bimetal element 66 is bent at an angle to form a foot 61 with a radius between the foot and the substantially vertical portion thereof. The foot 61 of the bimetal element is secured to the base of the easing by a rivet 16 which also serves to secure a terminal conductor 14 to the outside of the easing. ".he terminal conductor 14 is provided with a screw 16 which forms a convenient means for electrically connecting the breaker in an electical circuit.

An adjusting screw 66 threadedly engagim the bimetal element at a point near its free end. is provided with a head I6 which cooperates with a projection 12 of the latch member 46 to actuate the latch member when the bimetal element deilects in response to overload currents.

The bimetal element 66 is connected in the circuit controlled by the breaker by means of a flexible shunt conductor I6, the circuit extending from the terminal conductor 66, through the rivet 26, contacts 26-24, the contact bar 22, flexible shunt conductor 16, the bimetal element 66, and the rivet 13 to the terminal conductor l4.

In order to prevent the bimetal element 66 from operating in response to sudden shocks or jarring forces to cause false opening of the breaker, there is provided a pair of shock-absorbing bimetal elements 11 and 16 disposed one on each side of the tripping bimetal element 66. The bimetal elements 11 and 16 are provided with feet disposed, respectively, below and above the foot 61 of the tripping bimetal element and rigidly eecured to the base of the breaker casing by the rivet 16. The bimetal elements 11 and 16 are disposed in intimate relation with the tripping bimetal 66 along the radius between the foot 61 and the vertical portion of the tripping bimetal element, and then diverge away from the tripping bimetal element. The bimetal elements 11 and 16 are then formed inwardly toward the tripping bimetal element 66 with their upper ends hearing against the tripping bimetal element substantially as illustrated. The bimetal elements 11 and 16 have the same characteristics as the tripping bimetal element 66 and the high expansion sides of each bimetal element are on the same side, that is, on the right-hand side as viewed in the drawing; consequently, all three bimetal elements 66, I1 and I6 will deflect in the same direction when heated in response to current flowing therethrough. Since the three bimetal elements have the same characteristics, all three will deflect the same amount with the ends of the bimetal elements 11 and I6 hearing against the bimetal element 66 in all positions to stabilize the latter against displacement in response to sudden shocks.

Upon the occurrence of an overload in the circuit controlled by the breaker, the bimetal structure 66, I1 and 16 will be heated, and, since the high expansion of each of the bimetal elements is on the same side, will deflect as a unit and actuate the latch member 46 to release the relenable member 46. When this occurs, the overcenter springs 64 acting through the toggle 4|62 moves the contact bar 22 to open position and rotates the releasable member 46 clockwise about the pivot l4. During this rotation of the releasable member 46 the pivot pin 46 passes to the right of the center line of the springs 64 whereupon the springs 64 act to collapse the toggle, and, at the same time move the actuating lever 56 and a handle 66 to an intermediate indicating position.

The handle 66 extends through an opening 61 in the casing 4 and is provided with an arcuate base portion 66 which lies adjacent the arcuate inner surface of the top wall of the casing to seal the opening 61. The handle 66 is operatively rearouses lated to the actuating levers I by means of the rivet 62 and the outer ends ll of the actuating levers but is prevented from becoming disengaged from the actuating levers I by engagement of the base portion 80 with the arcuate surface 82 of the casing.

In order to reset the breaker mechanism and reclose the contacts following an automatic tripping operation, the handle 85 is first moved to the off position to reengage the releasable member in with the latch 44. In order to relatch the releasable member 40, the base portion 80 of the handle is provided with a pin BI which upon counterclockwise movement thereof, engages a projection 89 of the releasable member and moves the latter therewith to the relatched position. After the releasable member 40 is reset and relatched, the contacts may be closed by movement of the handle and the actuating levers 5O clockwise from the "off" position to the on position in the previously described manner.

According to the embodiment shown in Fig. 2, the latch member 48 of the Fig. l modification is omitted and the releasable member 40 is releasably restrained by means of an adjustable latchmember 9| rigidly secured to the free end of the tripping bimetal element SI. An adjusting screw 93 threadedly mounted in the bimetal element 56 is provided for adjusting the latch overlap thus varying the time required for the bimetal element to trip the breaker.

From the foregoing description, it will be apparent that there has been provided a circuit breaker of simple and rugged construction wherein the tripping bimetal element is supported against false tripping operation by means of angular, shock-resisting bimetal elements disposed one on each side of the tripping bimetal element, the shock-resistingbimetal elements having the same characteristic as the tripping bimetal element and maintaining their ends at all times against the tripping bimetal element to prevent false tripping of the breaker in response to sudden shocks.

Having described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the particular embodiment disclosed without departing from some of the essential features of the invention. It is, therefore, desired that the invention be interpreted as broadly as the prior art permits.

We claim as our invention:

1. In a circuit breaker comprising relatively movable contacts, a trip device for eii'ecting automatic opening of said contacts, said trip device comprising a current-carrying tripping bimetal element comprising a singl strip of bimetallic material, means rigidly mounting one end of said tripping bimetal element, and means comprising a pair of current-carrying bimetal elements disposed on opposite sides of said tripping bimetal and having a common mounting with said tripping bimetal element, and said pair of bimetal elements being spaced from said tripping bimetal element for a portion of their lengths, the free ends of said pair of bimetal elements bearing against opposite sides of said tripping bimetal element at a point substantially midway between the ends thereof to oppose false movement of said tripping bimetal element in response to sudden shocks. Y

2. In a circuit breaker comprising relatively movable contacts, a trip device for causing automatic opening of said contacts, said trip device comprising a single trip ing bimetal element. means rigidly mounting one end of said tripping bimetal element, and means comprising a pair of bimetal elements having a common mounting with said trippin bimetal element, said pair of bimetal elements being of substantially shorter length than said tripping bimetal element and disposed one on each side of said tripping bimetal element to oppose false movement of said tripping bimetal element in response to sudden shocks, said pair of bimetal elements being formed to first diverge in opposite directions away from said tripping bimetal element, and said pair of bimetal elements being then formed toward said tripping bimetal element so that their free ends at all times bear against opposite sides of said tripping bimetal element at a point substantially midway between the ends thereof.

3. In a. circuit breaker comprising relatively movable contacts, a, trip device comprising a tripping bimetal element connected to be traversed by the current of the circuit and operable in response to overload currents to effect opening of said contacts, and means comprising a pair of bimetal elements disposed one on each side of said tripping bimetal element to oppose movement of said tripping bimetal element in response to sudden shocks or jarring forces, said pair of bimetal elements being spaced from said tripping bimetal element to form an angle relative to said tripping bimetal element and having their free ends at all times bearing against said tripping bimetal element at a point substantially midway between the ends thereof.

4. A circuit breaker comprising relatively movable contact means, a trip device including a tripping bimetal element comprising a single strip of bimetallic material disposed to be heated by the current traversing the circuit of the breaker and operable when heated at predetermined amount in response to overload currents to effect opening of said contact means, and antishock means comprising a pair of bimetal elements spaced from said tripping bimetal for the major portion of their length and having their free ends disposed to bear against opposite sides of said tripping bimetal element at a point substantially intermediate the ends thereof to 0ppose movement of said bimetal element in response to shocks or vibratory forces.

5. A circuit breaker comprising relatively movable contact means, a. trip device comprising a single tripping bimetallic element connected to be traversed by the current of the circuit and operable when heated in response to overload currents to effect opening of said contact means, anti-shock means comprising bimetallic means connected in the circuit of the breaker in parallel relation with said bimetallic element to be heated in response to the current of the circuit, said bimetallic means being spaced from said tripping bimetallic element and having its free end engaging said tripping bimetallic element 'at'a point substantially intermediate the ends thereof to at all times oppose movement of said tripping bimetallic element in response to shocks, and said bimetallic means having the same characteristics' of said tripping bimetallic element and deflecting in the same direction and to the same extent therewith when heated in response to overload currents.

JULIUS TOTH.

GERALD J. FREESE.

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